This jar is a stand in for either source/javadoc for the annotations
used by the Checker Framework to type check source code.   The
checker-qual-compat.jar contains annotations that are compatible
with JDKs that do not support Type Annotations:
http://docs.oracle.com/javase/tutorial/java/annotations/type_annotations.html

For Checker Framework information visit:
http://types.cs.washington.edu/checker-framework/

